1. Field of the Invention
This invention relates to hydraulic valve lifters as used in internal combustion engines in general, and more particularly to a hydraulic valve lifter mounted in a rocker arm of a valve train assembly of the internal combustion engines.
2. Prior Art of the Invention
An example of a conventional hydraulic valve lifter of this type is disclosed in the Japanese patent laid open application No. 51 (1976) -89951. The above lifter includes a plunger reciprocably mounted in a cylinder formed in a rocker arm. Since a relief recess portion for a finishing machining process of the cylinder is positioned below a plunger stopper, a sliding portion of the plunger will be defined to be short. Therefore, a leak passage formed between the cylinder and the plunger will be defined to be short, an operating performance of the lifter will be deteriorated, and then noises and errors of a valve operating will be produced. In order to eliminate the above disadvantages, there has been proposed a method which diminishes an engaging clearance between the cylinder and the plunger by means of a precise machining process. However, due to the small clearance, the plunger will lack a smooth sliding movement, and then the cost of the machining process becomes very expensive.
In another conventional lifter wherein a stopper portion receiving a plunger is integrally formed in the rocker arm in a unitary body, the plunger will collide with the stopper portion when air is introduced into a pressure chamber. Accordingly, it may be difficult to secure the durability of the stopper portion.